It has long been commonplace to provide webs, such as paper webs, or sheets with lines of weakness whereby one part of the web or sheet may be separated from another. In most cases, lines of perforations are utilized for this purpose. The perforations are typically formed by a series of cuts extending through the web or sheet separated by ties, or unsevered portions of the web or sheet. Perforations heretofore used have ranged from rather coarse to so-called fine or "keen" perforations with the characterization being dependent upon the length of the tie along the line of perforation, and, to a lesser extent, the number of cuts per lineal inch of the line of perforation. In typical commercial practice, the finest perforation employed has a tie length in the range from about 0.024-0.040 inches and frequently, but not always, will be found as a result of forming the perforations with a blade having seventeen teeth per inch with each tooth having a cutting length of about 0.027 to 0.035 inches.
While such lines of perforation have functioned well for their intended purpose of allowing separation of webs along such lines, in many applications, they are not altogether acceptable. For example, and as is well known, in separating a business form along a line of perforation, the ties, during the process of being ruptured, and due to the fibrous nature of the paper, tend to pull outwardly of and extend past the straight cuts in the line of perforation with the consequence that an unsightly edge results. The edge is ragged as a result of the extended, ruptured ties and the relatively smooth cuts inbetween the ties. In cases where the forms are used for mass mailings or the like being processed on computer printers or tabulators, it is apparent to the recipient that the form is part of a mass mailing as opposed to a personal letter.
Consequently, to provide a more personalized appearance, business forms have been developed wherein an ordinary cut sheet business form, such as a letterhead, is "tipped on" to a paper carrier or web provided with control punch margins to facilitate computer processing. The carrier web is fed through the printer carrying with it the cut sheet letterhead which is then imprinted upon. Following the printing operation, the letterhead is removed from the carrier strip and stuffed into an envelope for mailing. The carrier strip is then discarded. Obviously, this procedure wastes approximately one half of the paper involved in the business form, which wastage could be avoided if the letterheads could be made up as continuous business forms with control punch margins and separated into individual form lengths with the control punch margins removed and still retain the appearance of a cut sheet. Furthermore, because of the nature of the paper used in some products, it is neccessary to provide a punched perforation as, for example, commonly used in postage stamps. In some papers, and dependent upon the direction of the line of perforation, the fibers may not run parallel to or with the line of perforation. Consequently, strong fibers in a tie running across the line of perforation may cause the tearing of the tie to "wander" off of the line of perforation and actually tear into the edge of the paper, again, resulting in an unsightly appearance. Consequently, punched perforations have been used in order to provide a large cut or hole into which the tear may wander when a strong fiber or fibers are approached so that the tear, upon encountering the next tie, is automatically realigned on the line of perforation. Of course, punched hole perforations provide an even more unsightly edge than those encountered when separating a web or the like along a line of perforation formed of cuts and ties. Moreover, the equipment required to form punched hole type perforations is quite expensive and extremely costly to maintain.
The present invention is directed to overcoming one or more of the above problems.